It is the objective of this ongoing study to identify variables in patient lavage fluid (BALF) and serum which are correlated with disease activity in pulmonary sarcoidosis, which can be used to predict course in the untreated patient and monitor response to therapy in the patient who receives treatment. This will be done in two ways. First, selected variables, measured in BALF and in serum, will be matched with clinical course in patients receiving no corticosteroids during an interval between evaluations. Second, patients, both treated and untreated, will be studied by repeat bronchoalveolar lavage (3-5 BAL, at 6 mo. intervals) to determine which variables return to normal in those patients who show clinical improvement, and which remain or become abnormal in patients who deteriorate or fail to improve. Putative markers of disease activity which will be evaluated include cell variables (total numbers, kinds, subsets, viability) and soluble protein components (immunoglobulins, acute phase reactants, mediators). Cell types and subsets will be identified using monoclonal antibodies for surface markers. Proteins will be measured by radial immunodiffusion against monospecific antibodies. Mediators will quantitated in bioassay for fibroblast proliferation. Our purpose is to identify very specific markers for both the alveolitic and fibrotic phases of interstitial lung disease, and to separate out those chemical and cellular changes which are associated with injury from those associated with repair. The contribution of demographic factors in determining the natural history of the disease will be evaluated within and between the North Carolina and Vermont patient groups.